A Brooklyn high school student was busted with a loaded gun magazine in his backpack Wednesday morning, police said.

The 20-year-old senior was going through a scanner as he entered Erasmus High School in Flatbush when the magazine was detected, according to police. 

The magazine was loaded with eight bullets, cops said. He was not carrying a gun.

The student was expected to receive a desk appearance ticket, police said. The charge was being determined.